Semiconductor device, a method for manufacturing a semiconductor device and an epitaxial growth substrate for a semiconductor device

ABSTRACT

A semiconductor device has a substrate body, an Al x Ga y In z N (x+y+z=1,x,y,z≧0) film epitaxially grown direct on the substrate body or epitaxially grown via a buffer layer on the substrate body, and a metal film provided on the rear surface of the substrate body. In the case of the manufacturing the semiconductor device, the substrate body is heated, by a heater, uniformly and efficiently through the thermal radiation of the heater.

BACKGROUND OF THE INVENTION

[0001] (1) Field of the Invention

[0002] This invention relates to a semiconductor device including a substrate body made of sapphire, SiC or GaN, etc. and an Al_(x)Ga_(y)In_(z)N film (x+y+z=1, x,y,z≧0) formed directly on the substrate body or formed via buffer film on the substrate body, a manufacturing method of the same and an epitaxial growth substrate for the same.

[0003] (2) Related Art Statement

[0004] At the present time, a semiconductor device such as a light emitting diode (LED), a laser diode (LD) or a field effect transistor (FET) is well known. Particularly, in the case of producing such a light emitting diode, an Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0) is epitaxially grown directly on the substrate body or epitaxially grown via buffer film on a substrate body made of sapphire, SiC or GaN, etc. Since the Al_(x)Ga_(y)In_(z)N film has its larger band gap, it can generate and emit a short wavelength light.

[0005]FIG. 1 is a cross sectional view showing a light emitting diode structure to emit a blue light having the Al_(x)Ga_(y)In_(z)N film. In the depicted light emitting diode, a GaN 2 film as a buffer layer is formed on a substrate body 1 made of a C-sapphire crystal (Al₂O₃) by a MOCVD method at low temperature, and a n-type Al_(x)Ga_(y)In_(z)N film 3 is epitaxially grown on the GaN film 2 by a MOCVD method. Then, a p-type Al_(x)Ga_(y)In_(z)N film 4 is epitaxially grown on the n-type Al_(x)Ga_(y)In_(z)N film 3 by a MOCVD method, and a low resistive Al_(x)Ga_(y)In_(z)N film 5 is epitaxially grown on the n-type Al_(x)Ga_(y)In_(z)N film 4 by a MOCVD method. Electrodes 6 and 7 are provided on the n-type Al_(x)Ga_(y)In_(z)N film 3 and the p-type Al_(x)Ga_(y)In_(z)N film 5, respectively.

[0006] In this case, the n-type Al_(x)Ga_(y)In_(z)N film 3 is grown with keeping the substrate body 1 and the buffer layer 2 at 1000° C. and over for improving the crystallinity and the flatness thereof. Therefore, heater structure and heater material having high thermal efficiency are developed in order to heat a given substance uniformly. The buffer layer 2 should be also composed of the above GaN film 2 or an AlN film formed at low temperature for improving the crystallinity and the flatness of the n-type Al_(x)Ga_(y)In_(z)N film 3. Moreover, a nitride layer formed at a surface of the substrate body may be employed as the buffer layer.

[0007] However, the substrate body may not often be heated to a desired temperature depending on film growth condition such as gas pressures and gas flow rates of raw materials. As a result, the n-type Al_(x)Ga_(y)In_(z)N film 3 can not have its good crystallinity and flatness. Moreover, the crystallinity and the flatness of the n-type Al_(x)Ga_(y)In_(z)N film 3 may be fluctuated due to the not uniform heating for the substrate body.

[0008] Particularly, in the case of forming an Al-rich Al_(x)Ga_(y)In_(z)N (x+y+z=1, x≧0.5, y, z≧0) film, the above-mentioned matters become conspicuous. First reason is because carrier gas (H₂, NH₃) with raw material gases must be flown at a fast flow rate of almost 1L/minute and over under a depressurized atmosphere of almost 100 Torr and below, for reducing the collision ratio of the elements of the raw material gases and thus, repressing, in the gas phase, the reaction between the elements of the Al raw material gas and the N raw material gas.

[0009] Second reason is because particularly in the case of forming the above Al-rich Al_(x)Ga_(y)In_(z)N (x+y+z=1, x≧0.5, y, z≧0) film, the substrate body is heated to 1100° C. and over, for improving its crystallinity and flatness through laterally epitaxial growth.

[0010] When the Al_(x)Ga_(y)In_(z)N film is formed at the above fast gas flow rate under the above depressurized atmosphere in a CVD apparatus, heat radiation degree from a surface of the substrate body is increased in the case of heating the substrate body with a heater. Therefore, the heater is required to be heated to a higher temperature than the desired substrate temperature by 100° C. and over. As a result, excess load is applied to the heater, and thus, the heater is degraded and the life time is shortened. Moreover, the surface of the substrate body may not be heated uniformly.

[0011] It is considered that the heating mechanism of the substrate body by the heater is originated from the thermal conduction due to the direct contact between the heater and the substrate body, the thermal conduction through the atmosphere gas composed of the above carrier gas, and the thermal conduction due to heat radiation. In this case, however, since the Al_(x)Ga_(y)In_(z)N film is formed under the depressurized atmosphere, the thermal conduction through the atmosphere gas does not almost contribute the heating mechanism. Moreover, since the substrate body is made of a transparent material such as sapphire and thus, does not almost absorb infrared light, the thermal conduction due to the heat radiation does not effectively contribute the heating mechanism. As a result, it is turned out that the heating mechanism is originated from the thermal conduction due to the direct contact between the heater and the substrate body. Therefore, if the substrate body is not set on a susceptor of the heater so as to contact the surface of the susceptor entirely, the substrate body is not heated to the desired temperature entirely. Moreover, since the carrier gas including the raw material gases is flown at the above fast flow rate, the heat radiation is brought about remarkably. Furthermore, the substrate body may be warped during the substrate body heating. Consequently, the substrate body is not heated sufficiently by the heater.

[0012] The above phenomena are observed when the Al_(x)Ga_(y)In_(z)N film is formed on a SiC substrate body or a GaN substrate body. Then, the above phenomena become conspicuous in a visible light-near infrared light range of 500 nm-2000 nm wavelength. As mentioned above, in the past, the surface of the substrate body is not heated uniformly under the condition of the fast gas flow rate, the depressurized atmosphere or the high film growth temperature-film forming, and thus, the Al_(x)Ga_(y)In_(z)N film can not have its good crystallinity and flatness. Then, excess load is applied to the heater, and thus, the life time of the heater is shortened.

SUMMARY OF THE INVENTION

[0013] It is an object of the present invention to provide a semiconductor device having, on a substrate body, an Al_(x)Ga_(y)In_(z)N film (x+y+z=1,xy,z≧0) with its good crystallinity and flatness through a small amount of defect.

[0014] It is another object of the present invention to provide a manufacturing method of the semiconductor device having the Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0) with its good crystallinity and flatness through uniform heating for the substrate body.

[0015] It is still another object of the present invention to provide an epitaxial growth substrate suitable for the above semiconductor device.

[0016] This invention relates to a semiconductor device including a substrate body, at least one Al_(x)Ga_(y)In_(z)N (x+y+z=1,x,y,z≧0) film epitaxially grown direct on the main surface of the substrate body or epitaxially grown via a buffer layer on the main surface of the substrate body, and a metal film provided on the rear surface of the substrate body.

[0017] In a preferred embodiment of the semiconductor device of the present invention, the substrate body is made of a material having a transmissivity of 50% or more within a wavelength range of 400 nm-800 nm. Moreover, the metal film formed on the rear surface of the substrate body is made of a high melting point metal of almost 1200° C. and over such as W, Ta, Mo, Ti, Be, Mn.

[0018] Moreover, in another preferred embodiment of the semiconductor device of the present invention, an Al-rich Al_(x)Ga_(y)In_(z)N (x+y+z=1, x≧0.5, y, z≧0) film is formed on the substrate body. Then, the buffer layer is composed of the Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0).

[0019] This invention also relates to a method for manufacturing a semiconductor device including the steps of:

[0020] setting a substrate body with a metal film on the rear surface thereof into a CVD apparatus,

[0021] introducing raw material gases with a given carrier gas onto the main surface of the substrate body, and

[0022] heating the substrate body via the metal film, thereby to epitaxilly grow at least one Al_(x)Ga_(y)In_(z)N (x+y+z=1,x,y,z≧0) film directly on the main surface of the substrate body or via a buffer layer on the main surface of the substrate body.

[0023] In a preferred embodiment of the manufacturing method of the semiconductor device, total gas flow rate is set to 1L/minute or over. Moreover, the interior pressure of the MOCVD apparatus is set to 100 Torr or below. Then, a metal film having a high melting point of almost 1200° C. and over is formed on the rear surface of the substrate body. Particularly, the above condition is more suitable for manufacturing the Al_(x)Ga_(y)In_(z)N film having a 50 atomic % or over Al concentration (x≧0.5).

[0024] This invention also relates to an epitaxial growth substrate comprising a substrate body, at least one Al_(x)Ga_(y)In_(z)N (x+y+z=1,x,y,z≧0) film epitaxially grown directly on the main surface of the substrate body or epitaxially grown via a buffer layer on the main surface of the substrate body, and a metal film provided on the rear surface of the substrate body.

[0025] In a preferred embodiment of the epitaxial growth substrate of the present invention, the substrate body has a transmissivity of 50% or more within a wavelength range of 400 nm-800 nm. Moreover, the metal film formed on the rear surface of the substrate body is made of a high melting point metal of almost 1200° C. and over such as W, Ta, Mo, Ti, Be, Mn. Then, the buffer layer is composed of the Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0).

[0026] According to this invention, the substrate body is heated via the metal film formed on the rear surface thereof by the heater. Since the metal film absorbs infrared light, the substrate body is heated uniform by the heat radiation of the metal film, and thus, is heated to a desired temperature efficiently. Therefore, when the Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0) is formed on the substrate body, it can have its good crystallinity and flatness. Moreover, excess loaded may not be applied to the heater and the life time of the heater may be elongated.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] For better understanding of the present invention, reference is made to the attached drawings, wherein

[0028]FIG. 1 is a cross sectional view showing a conventional light emitting diode structure,

[0029]FIG. 2 is a cross sectional view showing a semiconductor device according to the present invention,

[0030]FIG. 3 is a graph showing the relation between a main surface temperature of a substrate body and a film growth pressure in a CVD apparatus, and

[0031]FIGS. 4a-4 c are cross sectional views showing successive steps in a manufacturing method of a semiconductor device according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032]FIG. 2 is a cross sectional view showing a semiconductor device to generate and emit a blue light according to the present invention. The depicted semiconductor device has a similar structure to the one shown in FIG. 1, fundamentally. An Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0) film 12 as a buffer layer is formed on a substrate body 11 made of a C-sapphire crystal (A1 ₂O₃) by a MOCVD method at low temperature, and an n-type Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0) 13 is epitaxially grown on the Al_(x)Ga_(y)In_(z)N film 12 by a MOCVD method. Then, a p-type Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0) 14 is epitaxially grown on the n-type Al_(x)Ga_(y)In_(z)N film 13 by a MOCVD method, and a low resistive Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0) 15 is epitaxially grown on the n-type Al_(x)Ga_(y)In_(z)N film 14 by a MOCVD method. Electrodes 16 and 17 are provided on the n-type Al_(x)Ga_(y)In_(z)N film 13 and the p-type Al_(x)Ga_(y)In_(z)N film 15, respectively.

[0033] Then, a high melting point metal film 18 made of W, Mo, Ta, Ti, Be, Mn or the like is formed on the rear surface of the sapphire substrate body 11. The metal film 18 has a high melting point of 1200° C. and over. Then, the thickness of the metal film 18 is set to 0.1 μm, for example. As a result, the metal film has a sufficient heat resistance for the heating process of the substrate body when forming the above Al_(x)Ga_(y)In_(z)N films.

[0034]FIG. 3 is a graph showing the relation between a main surface temperature of the substrate body and a film growth pressure in the CVD apparatus. In this case, the total flow rate of the raw material gas and the carrier gas is set to be 1L/minute, and the susceptor temperature is set to be 1150° C. The solid line designates the relation between the main surface temperature and the film growth pressure of a substrate body with a Ti film on the rear surface of the substrate body, and the broken line designates the relation between the main surface temperature and the film growth pressure of a substrate body without the Ti film.

[0035] In both of the above substrate bodies, the main surface temperature is decreased as the film growth pressure is decreased. However, the decreasing degree of the main surface temperature of the substrate body with the Ti film designated by the solid line is smaller than that of the substrate body without the Ti film designated by the broken line. For example, when the film growth pressure is set to be 100 Torr, the difference in the main surface temperatures between the substrate bodies with and without the Ti film approaches to 100° C. or over.

[0036] Therefore, by forming a metallic film such as the Ti film on the rear surface of the substrate body, the main surface temperature of the substrate body can be maintained at a higher temperature, irrespective of the film growth pressure. As a result, in the case of setting the film growth pressure to 100 Torr, for example, the heating temperature of the heater can be reduced by almost 100° C. if the substrate body has the Ti film on the rear surface thereof.

[0037]FIGS. 4a-4 c are cross sectional views showing successive steps in a manufacturing method of a semiconductor device according to the present invention. First of all, as shown in FIG. 4a, the high melting point metal film 18 is formed, for example in a thickness of 0.1 μm, on the rear surface 11 b of the C-sapphire substrate by sputtering.

[0038] Then, as shown in FIG. 4b, the sapphire substrate body 11 is set into a MOCVD apparatus 20 so that the metal film 18 can be opposed to a heater 22 via a susceptor 24. Then, the Al_(x)Ga_(y)In_(z)N film 12 is epitaxially grown on a main surface 11 a of the substrate body 11. The sapphire substrate body 11 is heated, by the heater 22, through the thermal conduction of the direct contact between the heater 22 and the sapphire substrate body 11 and the thermal radiation of the metal film 18. Therefore, the sapphire substrate body 11 is heated efficiently, and thus, heated to a desired temperature easily. Then, excess load for the heater 22 is reduced and the life time of the heater is elongated, which makes easy the maintenance of the MOCVD apparatus 20 including the heater 22 and makes the manufactures' costs for the semiconductor device reduced. carrier gas of H₂ or NH₃ including the raw material gases is set to almost 1L/minute, and the interior pressure of the MOCVD apparatus 20 is set to almost 100 Torr. In this case, very fast gas flow is brought about around the sapphire substrate body 11, and thus, large heat radiation may occur at the sapphire substrate body 11. However, since the sapphire substrate body 11 has the metal film 18 at the rear surface 11 b, it can be heated to the desired temperature through the direct contact thennal conduction and the thermal radiation without the excess load for the heater 22. As a result, the Al-rich Al_(x)Ga_(y)In_(z)N buffer layer 12 can have its good crystallinity and flatness.

[0039] Subsequently, as shown in FIG. 4c, the Al_(x)Ga_(y)In_(z)N films 12-15 are epitaxially grown by MOCVD methods.

[0040] Although the present invention was described in detail with reference to the above examples, this invention is not limited to the above disclosure and every kind of variation and modification may be made without departing from the scope of the present invention. For example, the substrate body 11 may be made of SiC, GaN or AlGaN/sapphire, instead of the above C-sapphire substrate. Moreover, the metal film 18 may be made of an alloy film or a nitride film of the above high melting point metal such as W, Mo, Ta, Ti, Be or Mn. And the semiconductor device may be applied for other semiconductor device such as ultraviolet light-emitting diodes, laser diodes and field effect transistors.

[0041] Moreover, in the semiconductor device of the present invention, the buffer layer 12 may be omitted. Then, the above metal film 18 may be removed after the semiconductor device is completed. Furthermore, the metal film 18 may be used as the electrode. Then, the metal film 18 may be made of an alloy material of the above high melting point metal, a nitride film having a high melting point of 1200° C. or over, an multilayered film composed of the above high melting point metal. The alloy film and the nitride film may have composition gradient therein.

[0042] Moreover, in the above embodiment, although the Al_(x)Ga_(y)In_(z)N film is epitaxially grown under a depressurized atmosphere of 100 Torr or below, it may be done under a normal pressurized atmosphere. Then, instead of the above MOCVD method, a HVPE method using a chlorine based gas may be employed.

[0043] As mentioned above, according to this invention, the semiconductor device having, on the substrate body, the Al_(x)Ga_(y)In_(z)N film (x+y+z=1,x,y,z≧0) with its good crystallinity and flatness through a small amount of defect can be provided. Therefore, the semiconductor device can be applied for various semiconductor devices such as light-emitting diodes, laser diodes, field effect transistors.

[0044] Moreover, the epitaxial growth substrate suitable for the above semiconductor device can be provided. Therefore, the above semiconductor device can be easily formed by epitaxial growth.

[0045] Moreover, the method suitable for manufacturing the above semiconductor device can be provided. According to the manufacturing method of the present invention, the substrate body is heated through the thermal radiation of the metal film provided on the rear surface thereof, and thus, heated to the desired temperature efficiently. 

1. A semiconductor device comprising a substrate body, at least one Al_(x)Ga_(y)In_(z)N (x+y+z=1,x,y,z≧0) film epitaxially grown direct on the main surface of the substrate body or epitaxially grown via a buffer layer on the main surface of the substrate body, and a metal film provided on the rear surface of the substrate body.
 2. A semiconductor device as defined in claim 1, wherein the metal film is made of a metallic material having a high melting temperature of 1200° C. and over.
 3. A semiconductor device as defined in claim 1 or 2, wherein the substrate body is made of a material having a transmissivity of 50% or over within a wavelength range of 400 nm-800 nm.
 4. A semiconductor device as defined in claim 1 or 2, wherein the one or over Al_(x)Ga_(y)In_(z)N film has 50 atomic % or over Al concentration (x≧0.5).
 5. A semiconductor device as defined in claim 1 or 2, wherein the buffer layer is made of an Al_(x)Ga_(y)In_(z)N (x+y+z=1,x,y,z≧0) film.
 6. A method for manufacturing a semiconductor device comprising the steps of: setting a substrate body with a metal film on the rear surface thereof into a CVD apparatus, introducing raw material gases with a given carrier gas onto the main surface of the substrate body, and heating the substrate body via the metal film, thereby to epitaxailly grow at least one Al_(x)Ga_(y)In_(z)N (x+y+z=1,x,y,z≧0) film directly on the main surface of the substrate body or via a buffer layer on the main surface of the substrate body.
 7. A method for manufacturing a semiconductor device as defined in claim 6, wherein the total gas flow rate including the raw material gases and the carrier gas is set to 1L/minute or over, and then, the at least one Al_(x)Ga_(y)In_(z)N (x+y+z=1, x, y, z≧0) film is epitaxially grown directly or via the buffer layer on the main surface of the substrate body.
 8. A method for manufacturing a semiconductor device as defined in claim 6 or 7, wherein the interior pressure of the CVD apparatus is set to 100 Torr or below, and then, the at least one Al_(x)Ga_(y)In_(z)N (x+y+z=1, x, y, z≧0) film is epitaxially grown directly or via the buffer layer on the main surface of the substrate body.
 9. A method for manufacturing a semiconductor device as defined in claim 6 or 7, wherein the one or over Al_(x)Ga_(y)In_(z)N film has 50 atomic % or over Al concentration (x≧0.5).
 10. A method for manufacturing a semiconductor device as defined in claim 6 or 7, wherein the metal film, provided on the rear surface of the substrate body, is made of a metallic material having a high melting point of 1200° C. and over.
 11. An epitaxial growth substrate comprising a substrate body, at least one Al_(x)Ga_(y)In_(z)N (x+y+z=1,x,y,z≧0) film epitaxially grown directly on the main surface of the substrate body or epitaxially grown via a buffer layer on the main surface of the substrate body, and a metal film provided on the rear surface of the substrate body.
 12. An epitaxial growth substrate as defined in claim 11, wherein the metal film, provided on the rear surface of the substrate body, is made of a metallic material having a high melting point of 1200° C. and over.
 13. An epitaxial growth substrate as defined in claim 11 or 12, wherein the substrate body is made of a material having a transmissivity of 50% or more within a wavelength range of 400 nm-800 nm.
 14. An epitaxial growth substrate as defined in claim 11 or 12, wherein the one or over Al_(x)Ga_(y)In_(z)N film has 50 atomic % or over Al concentration (x≧0.5). 